Malware, which is short for malicious software, is a type of software that is designed to damage or disable computers and computer systems. It can take the form of viruses, worms, trojans, spyware, adware, and more.
Malware can be used to steal personal information, delete files, or take control of a computer.
"Amateurs hack systems, professionals hack people."
-- Bruce Schneier, a renown computer security professional